Cor triatriatum sinister is a rare cardiac anomaly. It is characterized by the presence of a fibromuscular membrane in the left atrium, thus forming a proximal chamber receiving the pulmonary veins and a distal chamber communicating with the mitral valve and the left atrial appendage. This rare pathology tends to coexist with a persistent left superior vena cava, whereas the presence of an anomalous systemic venous return is unusual. In this article, we report successful treatment of a patient with cor triatriatum sinister who has an additional systemic venous return anomaly.